No date has been set for the poll which insiders say could take place on May 4 as voters across the country take part in council elections.

Former doctor Mrs Troughton, a volunteer for St John Ambulance, saw off competition from rival candidates, fellow local councillor Barbara Cannon and hospital campaigner Rachel Holliday in a vote at Egremont Market Hall.

“Gillian is a local councillor with a strong track record of getting things done for her community. She has campaigned tirelessly to maintain local hospital services.

“As a St John blue light ambulance driver, Gillian has seen first-hand the extent of the crisis caused by this Conservative government, which has chosen to fund tax cuts for the wealthiest instead of our health service.

“I am proud that Labour has selected a local candidate with such dedication to her community.”

The selection process was mired in controversy amid claims the influential GMB union could refuse to back Mrs Holliday after its preferred candidates failed to make the final shortlist.

Jamie Reed and his party leader rarely saw eye to eye (Image: PA)

Former Dunfermline and West Fife MP Thomas Docherty, who previously sat on the Commons Defence Committee, did not get on the final ballot.

The Tories tonight hit out at Mrs Troughton's selection, branding it "a victory for the hard left".

A party spokeswoman said: “It is clear Gillian Troughton is nothing more than a Corbyn puppet in a Labour Party that is too divided and incompetent to stand up and secure the future of Cumbria’s industry and jobs.

“Only the Conservatives can be trusted to deliver the vital investment that will mean more jobs and better services for ordinary working Cumbrians.”